Optical network power consumption mitigation

ABSTRACT

The described implementations relate a Passive Optical Network (PON). In one implementation, the PON includes an Optical Network Unit (ONU) that has at least one transmitter subsystem component and an associated optical transmitter. The at least one transmitter subsystem component may be configured to be in an enabled state during a timeslot period assigned to the ONU for transmitting an upstream data burst and a disabled state after the timeslot ends.

RELATED APPLICATIONS

This Application is a Non-Provisional Application of ProvisionalApplication 61/358,996, which was filed on Jun. 28, 2010. Priority ofthe Provisional Application is hereby claimed and the entire contents ofthe Provisional Application are incorporated herein by reference.

BACKGROUND

Passive Optical Networks (PONs) may be used as part of theimplementation of next-generation access networks. With the largebandwidth of optical fibers, PONs can accommodate broadband voice, data,and video traffic simultaneously. Moreover, PONs can be built withexisting protocols, such as Ethernet and Asynchronous Transfer Mode(ATM), which facilitate interoperability between PONs and other networkequipment.

Transmissions within a PON are typically performed between an OpticalLine Terminal (OLT) and Optical Network Units (ONUs). The OLT generallyresides in a Central Office (CO) and couples the optical access networkto a backbone, which can be an external network belonging to, forexample, an Internet Service Provider (ISP) or a local exchange carrier.The ONU can reside in the residence or workplace of a customer andcouples to the customer's network through a Customer-Premises Equipment(CPE).

PON communications can include downstream traffic and upstream traffic.Downstream traffic refers to the direction from an OLT to one or moreONUs, and upstream traffic refers to the direction from an ONU to theOLT. In the downstream direction, data packets may be broadcast by theOLT to all ONUs and are selectively extracted by their destination ONUs.In the upstream direction, the ONUs share channel capacity andresources, because there is generally only one link coupling the passiveoptical coupler to the OLT.

As the popularity of PONs increases, the number of deployed ONUs willincrease. As a result, the power consumption of each ONU can no longerbe ignored, and adding power mitigating features to ONU designs becomesincreasingly important.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference number in different instances in thedescription and the figures may indicate similar or identical items.

FIG. 1 illustrates an exemplary implementation of a Passive OpticalNetwork (PON).

FIG. 2 illustrates an exemplary implementation of an Optical NetworkUnit Transmission system.

FIG. 2A illustrates a detailed view of the laser driver introduced inFIG. 2.

FIG. 3 illustrates an exemplary downstream frame.

FIG. 4 illustrates an exemplary laser or optical transmitter activationand deactivation procedure.

FIG. 5 is an illustrative computing device that may be used to implementthe devices, modules, apparatuses, and other hardware.

DETAILED DESCRIPTION

The following description describes implementations related to using anoptical transmitter to transmit upstream data in a Passive OpticalNetwork (PON). In various implementations, the optical transmitter maybe designed to mitigate power consumption. For example, the opticaltransmitter may be designed to receive signals that may be used toenergize or power on transmitter components downstream from the opticaltransmitter at some advance time before an upstream timeslot assignedthereto is to occur. Advance energizing or powering on of thetransmitter components of the optical transmitter may be configurable totake into consideration various optical transmitter types, aging ofcomponents in the transmitter, temperature variations, and the like. Theoptical transmitter may also be designed to receive instructions thatcause the optical transmitter to transmit an upstream data burst aboutor at the start of the upstream timeslot. Furthermore, the opticaltransmitter may be designed to receive instructions that cause thetransmitter components to power down or enter a reduced power operatingmode at the end or near the end of the upstream timeslot. Enabling thetransmitter components of the optical transmitter a determined timebefore the beginning of an assigned timeslot duration may reduce theamount of power consumed by apparatuses and devices deployed in the PON.Similarly, disabling the transmitter subsystem and components of theoptical transmitter after a timeslot ends may reduce the amount of powerconsumed by apparatuses and devices deployed in the PON

FIG. 1 illustrates an exemplary implementation of a PON 100. The PON 100may include Optical Network Units (ONUs) 102, 104 and 106 coupled to anOptical Line Terminal (OLT) 108 via an optical splitter 110. Trafficdata transmission may be achieved, for example, by using Ethernet framesreceived and transmitted over two optical wavelengths, respectively, onefor the downstream direction and another for the upstream direction.Downstream transmission from OLT 108 may be broadcast to all ONUs 102,104 and 106. Each ONU 102, 104 and 106 may filter its respective dataaccording to various known techniques. The ONUs 102, 104 and 106 maytransmit respective upstream data to the OLT 108 during differenttimeslots allocated by the OLT 108 for each ONU 120. The splitter 110may be used to split a single line into multiple lines.

PONs may be classified into one of the following: an ATM PON (APON), aBroadband PON (BPON), an Ethernet PON (EPON or GE-PON), and a GigabitPON (GPON). The APON uses the ATM protocol; the BPON is designed toprovide broadband services over an ATM protocol; the EPON accommodatesan Ethernet protocol; and the GPON is utilized when accommodating boththe ATM protocol and the Ethernet protocol. Each type of PON is astandardized technology. The PON 100 illustrated in FIG. 1 may be such astandardized PON, or a PON that has yet to be standardized by a standarddetermining body.

FIG. 2 illustrates an exemplary implementation of an ONU transmissionsystem 200. The ONUs 102, 104 and 106 may be implemented to include atleast the ONU transmission system 200 illustrated in FIG. 2. Some or allof the elements and modules illustrated in FIG. 2 may be integrated onone chip. Alternatively, some or all of the elements illustrated may bediscrete elements associated with one or more chips.

The ONU transmission system 200 may include a processor 202. A storage204, a frame generator 208 and a laser driver, transmit physical layeror optical driver 210 may be coupled to the processor 202. The laserdriver 210 may be coupled to a laser 212. The laser driver 210 may becapable of putting the laser 212 in an active or inactive state.Furthermore, the laser driver 210 may include circuitry that may beenabled, in preparation for upstream transmission of data, some periodof time before the laser 212 is activated to transmit data. Suchcircuitry may also be disabled after the laser 212 has completed a databurst transmission. The laser 212 may be a laser diode or other type ofoptical transmission apparatus.

The ONU transmission system 200 may also include a prediction engine214. The prediction engine 214 may be coupled to the storage 204, theframe generator 208 and the laser driver 210. The prediction engine 214may send instructions to the laser driver 210 that cause the laserdriver 210 to instruct the laser 212 to transition from an inactivestate to an active state, or vice versa. Furthermore, the predictionengine 214 may send instructions to the laser driver 210 to prepare orpower up various circuitry of the laser driver 210 prior to activatingthe laser 212 to transmit data. The prediction engine 214 may also sendinstructions to the laser driver 210 to power down various circuitry ofthe laser driver 210 after deactivating the laser 212. The predictionengine 214 may also receive or access information in the storage 204 andthe frame generator 208. The prediction engine 214 may use some of allof the information to derive the instructions that the engine 214 sendsto the laser driver 210. The laser driver 210 may incorporate a powersupply that provides voltage to the laser driver 210 and its associatedcircuitry. The power supply may be an integral part of the laser driver210, or an external device. Furthermore, the prediction engine 214 mayprovide software enabled instructions to the laser driver 210 to enablecontrol of the power supply. Alternatively, the prediction engine 214may provide software enabled instructions directly to the power supplyto achieve the transition from an inactive state to an active state, orvice versa.

The frame generator 208 may generate upstream data frames that are fortransmission to the OLT 108. These upstream data frames may be sent tothe laser driver 210, which in turn may transmit the upstream dataframes to the OLT 108 via the laser 212. In one implementation, theupstream data frames are transmitted to the OLT 108 in bursts, whereeach upstream data frame has a burst length defined by, for example, anupstream bandwidth map.

FIG. 2A illustrates an exemplary detailed view of the laser driver 210introduced in FIG. 2. The laser driver 210 may include subsystemcomponents, such as, a control logic 220, a modulation module 222 and alaser enable module 224. The control logic 220 may be coupled to theprediction engine 214. The modulation module 222 and the laser enablemodule 224 may each be coupled to the laser 212. Those of skill in theart understand that the subsystem components may also include clocktrees, data serializers and other active components and circuitelements.

The control logic 220 may generate control and data signals that arecommunicated to the modulation module 222. These signals may cause themodulation module 222 to generate a modulation current that provides aburst of upstream data to the laser 212. The control logic 220 may alsogenerate a control signal that causes the laser enable module 224 togenerate a laser enable current that activates the laser 212 to producean optical output signal to optically transmit the burst of upstreamdata associated with the modulation current. Signals generated by thecontrol logic 220 may also cause the modulation module 222 and the laserenable module 224 to enter into a powered down state or a reduced powerstate.

The modulation module 222 may include a current source that generatesthe modulation current. In one implementation, the modulation current isswitched through a laser diode after being generated by the currentsource. A current control circuit may be coupled to the current source.This current control circuit may be controlled by the control logic 220in a stepwise manner to adjust a level of the modulation current. Thelaser enable module 224 may include a current source that generates thelaser enable current. In one implementation, the laser enable current isswitched through a laser diode after being generated by the currentsource. A current control circuit may be coupled to the current sourceof the laser enable module 224. This current control circuit may becontrolled by the control logic 220 in a stepwise manner to adjust alevel of the laser enable current.

FIG. 3 illustrates an exemplary downstream frame 300. The downstreamframe 300 may be associated with the PON 100. The downstream frame 300may include a header 302, an upstream bandwidth map 304 and a payload306. The upstream bandwidth map 304 may include an ONU ID field 308, astart field 310 and an end field 312. The fields 308-312 are used toindicate a start position and an end position of each ONU upstreamtimeslot. Each ONU (e.g., ONUs 102-106) is to send an upstream burstpacket to the OLT 108 in accordance with the timeslot informationassigned thereto. For example, the upstream bandwidth map 304 mayinclude timeslot information for the ONU 102. The start field 310 mayidentify that the start position of the upstream timeslot is the initialor 1^(st) timeslot and the end field 312 may identify that the endposition of the upstream timeslot is the 100^(th) timeslot. Using thisinformation, the ONU 102 is aware that it may send one or more upstreamburst packets starting at the 1^(st) timeslot and ending at the 100^(th)timeslot.

The upstream bandwidth map 304 may be stored in the storage 204.However, the exemplary downstream frame 300 does not necessarily includethe upstream bandwidth map 304. Rather, the downstream frame 300 maycarry the ONU ID field 308, the start field 310 and the end field 312 inother portions of the frame 300 or in another packaged format other thanthe upstream bandwidth map 304. Furthermore, the information carried infields 308-312 may be included in a plurality of downstream frames orother frame types.

Specifics of exemplary procedures are described below. However, itshould be understood that certain acts need not be performed in theorder described, and may be modified, and/or may be omitted entirely,depending on the circumstances. Moreover, the acts described may beimplemented by a computer, processor or other computing device based oninstructions stored on one or more computer-readable storage media. Thecomputer-readable storage media can be any available media that can beaccessed by a computing device to implement the instructions storedthereon. The exemplary procedures described below may reference one ormore of the exemplary devices described in FIGS. 1-3. Therefore, one ormore of the devices and information illustrated in FIGS. 1-3 may used toimplement the described procedures. However, the referenced devices arenot limiting of the described procedures.

FIG. 4 illustrates an exemplary optical transmitter subsystem activationand deactivation procedure. At block 402, a start position of anupstream timeslot and an end position of the upstream timeslot may bedetermined. In one exemplary embodiment, the predictive engine 214obtains the start position and end position of the upstream timeslotfrom the storage 204. The predictive engine 214 may estimate ordetermine temporal related information that coincides with the startposition and the end position of the upstream engine 214. Such temporalrelated information may take into consideration how long it takes theoptical transmitter subsystem components (e.g., the modules 302 and 304)to power up to a ready state such that the modulation and laser enablecurrents may be supplied to the laser 212 in sufficient time to causethe laser 212 to transmit an upstream data burst at the start positionof the upstream timeslot. In one implementation, the optical transmittersubsystem components may include some or all of the componentsassociated with a transmit physical layer.

At block 404, an optical transmitter (e.g., the laser 212) is enabled ator about at a time the start position of the upstream timeslot is tooccur. In one exemplary embodiment, the predictive engine 214 sendsinstructions to the laser driver 210 that may be used thereby to causethe laser 212 to transmit an upstream data burst at the start positionof the upstream timeslot. These instructions may be based on informationreceived or otherwise obtained from the storage 204. The instructionsfrom the predictive engine 214 may also enable the laser driver 210 todisable the laser 212 at the end position of the upstream timeslot, asis indicated at block 406.

At block 404, the predictive engine 214 may also send instructions tothe laser driver 210 that may be used by the control logic 220 to poweron, increase supplied power to, or “wakeup” various optical transmittersubsystem components at some calculated, determined or estimated timebefore biasing the laser 212 to transmit an upstream data burst. Suchtransmitter subsystem components may include, for example, the currentsource associated with the modulation module 222, the current sourceassociated with the laser enable module 224, clock trees associated withthe laser driver 210, and the current control circuits in the modules302 and 304. The calculated, determined or estimated time generated bythe predictive engine 214 takes into account when the laser 212 must beenabled to transmit the upstream data burst and how long it will takethe optical transmitter subsystem components to reach the necessaryoperational state sufficient to supply the necessary current to thelaser 212. Depending on the implementation and design particulars, itmay be desirable to reduce an amount of energy or power consumed by theoptical transmitter subsystem components by a particular percentage, asopposed to fully or nearly fully powering down those components. In suchan implementation, the calculated, determined or estimated timegenerated by the predictive engine 214 may be shorter as compared to acalculated, determined or estimated time required to energize or poweron subsystem components that are substantially in a powered off state.

As should be readily understood from the foregoing, the predictiveengine 214 may supply instructions that include distinct instructionsets. One instruction set indicates when the laser driver 210 is tocause the laser 212 to transmit an upstream data burst and when thelaser 212 should be disabled. Another instruction set instructs thecontrol logic 220 to, in anticipation of an impending upstream databurst transmission, wake, energize or other otherwise enable one or moretransmitter subsystem components so that those components are ready tosupply the necessary currents to the laser 212 at or around the startposition of the upstream data burst. Furthermore, the anotherinstruction set may include instructions that instruct the control logic200 to reduce the power consumed by the subsystem components once thelaser 212 completes the upstream data burst. The instructions toactually transmit an upstream data burst may originate from, forexample, the frame generator 208 as opposed to the predictive engine214.

FIG. 5 is an illustrative computing device that may be used to implementthe devices, modules, apparatuses, processes, procedures and hardwarediscussed herein. In a very basic configuration, the computing device500 includes at least one processing unit 502 and system memory 504.Depending on the exact configuration and type of computing device 500,the system memory 504 may be volatile (such as RAM), non-volatile (suchas ROM and flash memory) or some combination of the two. The systemmemory 504 typically includes an operating system 506, one or moreprogram modules 508, and may include program data 510.

For the present implementations, the program modules 508 may realize thevarious elements described as being associated with the architecturesand implementations herein. Other modules and device functionalitiesdescribed herein may also be part of the program modules 508. Thecomputing device 500 may have additional features or functionality. And,the computing device 500 may also include additional data storagedevices (removable and/or non-removable) such as, for example, magneticdisks, optical disks, or tape. Such additional storage is illustrated inFIG. 5 by removable storage 520 and non-removable storage 522. Computerstorage media may include volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information, such as computer readable instructions, data structures,program modules, or other data. The system memory 506, removable storage520 and non-removable storage 522 are all examples of computer storagemedia. Thus, computer storage media includes, but is not limited to,RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM,digital versatile disks (DVD) or other optical storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to store thedesired information and which can be accessed by computing device 500.Any such computer storage media may be part of the device 500. Computingdevice 500 may also have input device(s) 524 such as keyboard, mouse,pen, voice input device, and touch input devices. Output device(s) 526such as a display, speakers, and printer, may also be included. Thesedevices are well known in the art and need not be discussed at length.

The computing device 500 may also contain a communication connection 528that allow the device to communicate with other computing devices 530,such as over a network. The communication connection may also enable thecomputing device 500 to wirelessly communicate with many different typesof wireless service providers and medium.

Various modules and techniques may be described herein in the generalcontext of computer-executable instructions, such as program modules,executed by one or more computers or other devices. Generally, programmodules include routines, programs, objects, components, datastructures, and so forth, for performing particular tasks or implementparticular abstract data types. These program modules and the like maybe executed as native code or may be downloaded and executed, such as ina virtual machine or other just-in-time compilation executionenvironment. Typically, the functionality of the program modules may becombined or distributed as desired in various embodiments. Animplementation of these modules and techniques may be stored on ortransmitted across some form of computer readable media.

For the purposes of this disclosure and the claims that follow, theterms “coupled” and “connected” have been used to describe how variouselements interface. Such described interfacing of various elements maybe either direct or indirect. Although the subject matter has beendescribed in language specific to structural features and/ormethodological acts, it is to be understood that the subject matterdefined in the appended claims is not necessarily limited to thespecific features or acts described. Rather, the specific features andacts are disclosed as preferred forms of implementing the claims. Thespecific features and acts described in this disclosure and variationsof these specific features and acts may be implemented separately or maybe combined.

The invention claimed is:
 1. A method configured to control an opticaltransmitter subsystem, the method comprising: determining a startposition of an upstream timeslot for transmitting optical signals;determining a first amount of time necessary to enable one or moremodulation current sources to transition from a reduced energy state toa ready state where the one or more modulation current sources arecapable of providing modulation currents to the optical transmitter;generating a first set of instructions that instructs the one or moremodulation current sources to activate at a first time corresponding tothe first amount of time prior to the start position of the upstreamtime slot; providing the first set of instructions to a modulationmodule that includes the one or more modulation current sources;determining a second amount of time necessary to enable one or morelaser enable current sources to transition from the reduced energy stateto the ready state where the one or more laser enable current sourcesare capable of providing a bias current to the optical transmitter;generating a second set of instructions that instructs the one or morelaser enable current sources to activate at a second time correspondingto the second amount of time prior to the start position of the upstreamtime slot; and providing the second set of instructions to a laserenable module that includes the one or more laser enable currentsources.
 2. The method according to claim 1, further comprising:generating a third set of instructions to disable the one or moremodulation current sources substantially at an end position of theupstream timeslot; and providing the third set of instructions to themodulation module.
 3. The method according to claim 1, furthercomprising obtaining the start position and an end position from adownstream data transmission.
 4. The method according to claim 1,wherein the one or more modulation current sources are associated withlaser driver used in a Passive Optical Network (PON).
 5. The methodaccording to claim 1, wherein the one or more modulation current sourcesare associated with an Optical Network Unit (ONU).
 6. The methodaccording to claim 1, wherein the first amount of time is different fromthe second amount of time.
 7. The method according to claim 1, furthercomprising: generating a fourth set of instructions to disable the oneor more laser enable current sources substantially at an end position ofthe upstream timeslot; and providing the fourth set of instructions tothe laser enable module.
 8. An apparatus, comprising: a storage circuitconfigured to store a start position of an upstream timeslot to transmitoptical signals; a prediction engine circuit configured to: receive thestart position stored in the storage circuit; determine a first amountof time necessary to enable at least one modulation current source of anoptical transmitter to transition from a reduced energy state to a readystate sufficient to supply a modulation current to the opticaltransmitter; generate a first set of instructions that instructs the atleast one modulation current source to activate at a first timecorresponding to the first amount of time prior to the start position ofthe upstream time slot; and provide the first set of instructions to amodulation module that includes the at least one modulation currentsources; determine a second amount of time necessary to enable one ormore laser enable current sources to transition from the reduced energystate to the ready state where the one or more laser enable currentsources are capable of providing a bias current to the opticaltransmitter; generate a second set of instructions that instructs theone or more laser enable current sources to activate at a second timecorresponding to the second amount of time prior to the start positionof the upstream time slot; and provide the second set of instructions toa laser enable module that includes the one or more laser enable currentsources.
 9. The apparatus according to claim 8, wherein the opticaltransmitter is configured to transmit an upstream data burst at thestart position of the upstream timeslot.
 10. The apparatus according toclaim 8, wherein the storage circuit and the prediction engine circuitare integrated on a single chip.
 11. The apparatus according to claim 8,wherein the prediction engine circuit is configured to: generate a thirdset of instructions to disable the at least one modulation currentsource substantially at an end position of the upstream timeslot; andprovide the third set of instructions to the laser enable module. 12.The apparatus according to claim 8, wherein the first amount of time isdifferent from the second amount of time.
 13. The apparatus according toclaim 8, wherein the prediction engine circuit is configured to:generate a fourth set of instructions to disable the one or more laserenable current sources substantially at an end position of the upstreamtimeslot; and provide the fourth set of instructions to the laser enablemodule.